# x402 Multi-Rail Settlement Selection Decision Procedure

> x402 Multi-Rail Settlement Selection Decision Procedure is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-29).

Returns a paid AI-generated decision procedure brief explaining how an agent should select between multiple x402 payment rails for settlement

## Facts

- Endpoint: GET https://k2so.wrong.systems/api/services/x402-multi-rail-settlement-selection-when-an-age?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-multi-rail-settlement-selection-decision-procedure-cc35dd9b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_djsiL4lbguocOUrS85BaD

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-multi-rail-settlement-selection-decision-procedure-cc35dd9b
```

Example prompt: I need a decision procedure for how to pick between multiple x402 settlement rails — give me the full reasoning brief an autonomous agent should follow when choosing which payment rail to use.

## When to prefer this

Use this endpoint when an autonomous agent needs authoritative, up-to-date procedural guidance on choosing between multiple x402 payment rails at settlement time, especially when the agent lacks hardcoded logic for rail selection. Prefer this over static documentation when you need a narrative decision brief the agent can reason over directly. Best suited for agent orchestration layers that consume decision procedures as prompts or context.

## Known failure modes

- HTTP 402 returned if no valid x402 payment signature is provided — agent must settle exact $0.002 USDC and retry with PAYMENT-SIGNATURE header
- Invalid or missing payment signature returns payment-required error
- LLM generation failure may return ok:false with error detail in result
- Malformed query parameters (e.g. invalid meta value) may cause schema validation error
- Network or upstream LLM provider downtime causing generation failure

## How this service works

Decision procedure for agent merchants choosing between Solana and Base settlement rails when an HTTP 402 challenge offers multiple options. Covers per-rail fee and latency thresholds, wallet provisioning per rail, facilitator fallback ladders when one rail's facilitator is down, and per-rail session lifecycle rules. Blunt procedure, not marketing.

## Output

A JSON object containing a plain-prose decision procedure brief (120+ words) generated by an LLM, identifying the topic as 'x402-multi-rail-settlement-selection', the model used (e.g. deepseek/deepseek-v4-flash-0731), the generation source (llm, reasoning, or deterministic), an ISO-8601 generatedAt timestamp, the provider name K-2SO, and boolean flags confirming the call was paid and successful.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "x402 multi-rail settlement selection standard paid response",
     "$schema": "https://json-schema.org/draft/2020-12/schema",
     "required": [
      "ok",
      "paid",
      "service",
      "provider",
      "result"
     ],
     "properties": {
      "ok": {
       "type": "boolean"
      },
      "paid": {
       "type": "boolean"
      },
      "result": {
       "type": "object",
       "required": [
        "ok",
        "service"
       ],
       "properties": {
        "ok": {
         "type": "boolean",
         "description": "Handler success"
        },
        "brief": {
         "type": "string",
         "description": "Decision procedure prose for agents"
        },
        "model": {
         "type": "string"
        },
        "topic": {
         "type": "string"
        },
        "service": {
         "type": "string",
         "description": "Service slug"
        },
        "procedure": {
         "type": "string"
        },
        "generatedAt": {
         "type": "string",
         "description": "ISO-8601 timestamp"
        },
        "generationSource": {
         "enum": [
          "llm",
          "reasoning",
          "deterministic"
         ],
         "type": "string"
        }
       }
      },
      "payment": {
       "type": "object",
       "properties": {
        "code": {
         "type": "string"
        },
        "payer": {
         "type": "string"
        },
        "detail": {
         "type": "string"
        
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "paid": true,
  "result": {
   "ok": true,
   "brief": "plain prose decision procedure (120+ words)",
   "model": "deepseek/deepseek-v4-flash-0731",
   "topic": "string topic",
   "service": "x402-multi-rail-settlement-selection-when-an-age",
   "procedure": "same as brief",
   "generatedAt": "2026-01-01T00:00:00.000Z",
   "generationSource": "deterministic"
  },
  "service": "x402-multi-rail-settlement-selection-when-an-age",
  "provider": "K-2SO"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-multi-rail-settlement-selection-decision-procedure-cc35dd9b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from k2so.wrong.systems](https://www.zero.xyz/host/k2so.wrong.systems/llms.txt)